The present invention concerns a process for the preparation of 5-substituted-8-alkoxy[1,2,4]triazolo[1,5-c]pyrimidin-2-amines.
U.S. Pat. No. 6,005,108 describes certain substituted 5,8-disubstituted-[1,2,4]-triazolo[1,5-c]pyrimidin-2-amine compounds and their use as intermediates for the preparation of sulfonamide herbicides. 5,8-Dimethoxy[1,2,4]triazolo[1,5-c]pyrimidin-2-amine is a useful intermediate for the preparation of penoxsulam. Monatsh. Chem. 1983, 114, 789 describes the preparation of certain (amino)carbonothioylcarbamates followed by their reaction with hydroxylamine and subsequent cyclization to [1,2,4]triazolo[1,5-a]-pyrimidin-2-amines. WO 2009/047514 A1 describes the preparation of certain (amino)-carbonothioylcarbamates followed by their reaction with hydroxylamine and subsequent cyclization to [1,2,4]triazolo[1,5-a]pyridine and [1,2,4]triazolo[1,5-c]pyrimidine compounds. U.S. Pat. No. 6,559,101 B2 describes the preparation of certain (amino)carbonothioylcarbamates followed by their reaction with hydroxylamine and subsequent cyclization to pyrimidine substituted [1,2,4]triazolo[1,5-a]pyrimidin-2-amines.
5,8-Dimethoxy[1,2,4]triazolo[1,5-c]pyrimidin-2-amine is produced from 2,4-dichloro-5-methoxypyrimidine in a multistep process that involves both hydrazine and a cyanogen halide. Hydrazine presents a severe explosion hazard and is toxic by ingestion, inhalation and skin adsorption. It is classified as a carcinogen and has a TLV of 0.1 ppm in air. Cyanogen halides are highly irritating and very poisonous. It would be advantageous to produce 5-substituted-8-alkoxy[1,2,4]triazolo[1,5-c]pyrimidin-2-amines efficiently and in high yield by a manufacturing process that avoids hydrazine and cyanogen halide.